JavaScript 将日期设置为 x 的开头

Question

我正在开发一个 fn，它将日期设置为分钟/小时/天/周/月/季度/年的开始。

我从本周开始做如下事情:

var date = new Date(),
    day = d.getDay(),
    // adjust when day is sunday
    diff = d.getDate() - day + (day == 0 ? -6 : 1);

    var updatedDate = new Date(date.setDate(diff);

但我想知道是否有更好的方法(或框架)来完成此类事情？

Answer 1

这是迄今为止我能想到的最好的:

function beginningOf(period, date) {
    date = new Date(date.valueOf()); // copy date

    if (period === "year" || period == "quarter") {
        date.setMonth(period === "quarter"
                      ? 3 * Math.floor(date.getMonth() / 3)
                      : 0);
        period = "month"; // now round down to the start of this month
    }

    if (period === "month" || period === "week") {
        date.setDate(period === "week"
                     ? date.getDate() - date.getDay() // Sunday is the first day, adjust to suit
                     : 1);
        period = "day"; // now round dow to the start of this day
    }

    // intentional switch fall-through
    switch (period) {
        case "day":
            date.setHours(0);
        case "hour":
            date.setMinutes(0);
        case "minute":
            date.setSeconds(0);
            date.setMilliseconds(0);
    }

    return date;
}

参见http://jsfiddle.net/alnitak/6hj9u/

这是一个比我预想的稍微难一点的问题......